631640 has 16 divisors (see below), whose sum is σ = 1421280. Its totient is φ = 252640.

The previous prime is 631619. The next prime is 631643. The reversal of 631640 is 46136.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (631643) by changing a digit.

631640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7856 + ... + 7935.

It is an arithmetic number, because the mean of its divisors is an integer number (88830).

2⁶³¹⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

631640 is an abundant number, since it is smaller than the sum of its proper divisors (789640).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

631640 is a wasteful number, since it uses less digits than its factorization.

631640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15802 (or 15798 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 20.

The square root of 631640 is about 794.7578247491. The cubic root of 631640 is about 85.8005111149.

Adding to 631640 its reverse (46136), we get a palindrome (677776).

The spelling of 631640 in words is "six hundred thirty-one thousand, six hundred forty".